Process for the pyrolytic conversion of normally gaseous aliphatic hydrocarbons



March 1, 1932. G. G. oBERr-'ELL ET AL PROCESS FOR THE PYROLYTIC CONVERSION OF NORMALLYV GASEOUS ALIPHATIC HYDROOARBONS Filed May 24, 1928 2 Sheets-Sheet EN n n ATTORNEY f' GASEOUS ALIPHATIC HYDROCARBONS Filed May 24, 1928 G G OBERFELL ET AL PROCESS FOR THE PYROLYTIC CONVERSION OF NORMALLY March l, 1932.

INVENTOR ATTORNEY Patented Mar. `l, 1932. u

. UNITED STATES GEORGE e. OBEEEELL AND JEssE A GUYEB., or BAHTLEsvILLH, OKLAHOMA, Assreirons To PHILLIPS PETROLEUM COMPANY, or BAETLESVILLE, OKLAHOMA, A CORPORA- 'HON or DELAWARE PB .ocEss EOH'THE rHoLYrIc oONvERsION or NORMALLY GAsEoUs f HYDHocAaBoNs ALDHIATIC lApplication led May 2.4, 1928. Serial No. 280.331.

This invention relates to improvements in processesl for the thermal decomposition of gaseous hydrocarbons' such as occur in natural gas and the like.

The primary object of the invention is to furnish a process in which lighthydrocarbons such as Occur in natural gas may be converted into heavier hydrocarbons of the aromatic -f -exchanger D where such materialK loses partV series. y Another object of the invention is to provide a process designed to crack natural gas or the like for reforming the gas and producing substantial quantities of liquid hydrocarbons.

A still further object is to furnish a process in which substantially pure natural gas constituents such as ethane, propane, and butane, may be reformed and partially converted into liquid hydrocarbons.

It is also an object of the invention to 'provide a system in which gaseous hydro-` carbons after a decom osition treatment may be separated into residue gas and liquid hydrocarbons, said residuegas being recycled for' the purpose of decomposing and extracting from the same, additionalamounts of liquid hydrocarbons. e Y

With the foregoing objects outlined and with. other objects in view which will appear as the descripiton proceeds, the invention consists 'in the novel features hereinafter de scribed in detail, illustrated in the accompanying drawingsy and more particularly pointed out in the appended claims. A

Referring to the drawings, Fig. 1 is a diagrammatic elevation ofan apparatus suitable for use in performing the process. Fig. 2 is a similar view of a modified heating device for'use in such system.

. The gas to be treated, whether formed of ture, and in G it is heated tothe reforming necessary length of'time to cause'Y the desired conversion.

From "he reaction chamber the reformed gas and the liquid Jhydrocarbons produced .i

are sent through a pipe H1 into the heat of its heat to the untreated gases passing by' way of pipe C and E to the heating coils F. The treated gases leave the heat exchanger by way of pipe H2 and iiow through a scrubber K of any desired character and from the latter the treated material passes through a pipe H3 into a benzol recovery plant L, in which the liquid hydrocarbons are separated from`the reformed lgas and discharged by way of outlet L1. d

`Some of the reformed gases pass of by way fof the pipe J to any suitable point of disposal and the remainder of the reformed gases are recycled through a 'conduit L2, which leads the same through any Suitable form of metering device A, back to the un-r treated gas line C.

It will be understood that valves are arranged in the pipe lines at the desired points to properlyicontrol the operations. The tubes `F and G are heated by products of combust-ion from gas burned in a combustion chamber M, and the products of combustion after passing through the furnace P escape to the atmosphere. through the stack N.

When this process and apparatus are employed in the treatment of substantially pure components (propane, for instance,) it differs from yother processes in that relatively fixed temperatures and velocities may be used.

Ina process using a mixture `of gases, say, ethane, propane, and butane, the synthesis is carriedout at a temperatureand time of exposure which will be an average of those most suitable for each individual component. The condition suitable for one component gas such as propane, can be easily determined and then used for all future operations.

Regardless of whether a single component or a multi-component gas is treated, the reactionchamber H should be maintained at a 100 temperature within a range of 1250o F. to

17 50 F. and the time of exposure ofthe products of the reaction should come within a range of 0.002 minutes to 10 minutes dependl ing upon the temperature maintained, the character of the gas treated, and the products desired. Conditions of this character will permit the production of substantial quantities of liquid hydrocarbons, and by substantial quantities is meant at least .5 of a gallon vto each 1000 cubic Vfeet lof gas treated.

The apparatus illustrated is preferably used for the treatment of hydrocarbon gases lighter than pentane, although there may be traces of the latter in the gas without any deleterious effect on the process.

The recycling step of the process may be used when a single component gas is treated or when a multi-component gas is treated, but it is preferably used when multi-component gases are subjected to the process.

When'multi-component gases are treated,

i such as butane and propane, or butane, profound that this permits the production of .larger quantities of liquidhydrocarbons.

pane, and ethane, the recycling will allow some or all of the gas to be twice subjected to decomposing conditions and it has been Instead of using the heating means shown at the left hand side of the reaction chamber in Fig. 1, it is obvious that the 'gases to be processed may be heated in various ways and by any other suitable means. In Fig. 2 another modification of the heating means is disclosed. In this assembly a combustion chamber A", is heated by a gas burner or the like. From the combustion chamber, the products of combustion iow through the heating chamber BX to the stack H".

.A coil Cx is arranged in the furnace and is connected by pipes DX to the heating medium space IX' of the reaction chamber E". Tubes K pass through the reaction chamber from top to bottom and convey through the latter the gases to be treated, which enter through FX and discharge through Gf. .l

By arranging a pump or the like Lx in one of the pipes D", an inert gas used as a heating medium for the reaction chamber may be circulated and in this way the temperature in the reaction chamber may be properly or accurately maintained.

The heating apparatus used in Fig. 1, and l l'Fahrenheit and t=time in minutes during which the gas is maintained at thetemperature T, subsequent to a rapid heating to that temperature, with rapid cooling upon expiration of cracking periodv t. A several fold increase in exposure time above that calculated by the formula results in little increase in yield of volatile oils, but tar and Carbon formation are thereby increased and the gas depleted in caloriic value. Gases whose vapor pressures fall between 25 to 500 pounds per square inch have been found to respond successfully to the process treatments described above, but the invention is not limited to such gases. The pressure range mentioned, however, has the advantage that it enables the process treatment to take place substantially under atmospheric pressure throughout.

In regard to said formula, it may be stated that experiments were conducted with the object of determining the rle of cracking -time as Well as temperature in producing an optimum yield of benzol. A gas of the composition Y Per cent Methane 18.6 Propane 44.7 Butane 36.7

was submitted to cracking in a non-catalytic silica tube under conditions suitable for the production of benzol. The experiments were conducted at atmospheric'pressure and the carbon, tar, benzol and gases were separately measured. The eifect of time and tempera'- ture on benzol yield is shown in the following table, in which time is expressed in minutes and benzol yield in gallons per thousand cubic feet of gas:

Tabla-Effect of time of cracking on benzol yield at several temperatures Time Yield 1292 F.

At a given temperature, the yield of benzol was observed to increase gradually as the cracking time increased, until a virtually maximum yield was developed. A several fold increase in time beyond the minimum nccessaryto develop a. virtually maximum yield caused little change in benzol yield, but

in temperature increasedfthe reaction velocity I substantially as expressed by the formula `Tv=124518o 10g.1`.t,

without greatly inluencingfthe sequence of whe'e T is th temperature in degrees F911' changes taking place during cracking. The maximum yield ofbenzol was roughly con# stant throughout 'the' rather wide temperature range studied within the time range appropriate to and unique for each temperature. The data of the table-showthe minimum time required to obtain a substantially optimum yield of benzol; at several temperatures within a rather wide range. The values are approximately 0.5 minutes at 1292 F., 0.2 minutes at 1382 F., 0.012`minutes` at 1562 F., andsomeivhat less than 0.003 minutes at 174.2o F. A A .Y

' These values may be used to determine a time-temperature relation which is expressed in a compact form by the equation in which T is temperature degrees Fahrenhelt, and t is time in mmutes. The tlme given by the formula is a minimum'valuefor the formation of a0 substantially maximum yield'of benzol.

In practice,` a reaction' time as much as several -fold greater may be used without loss in benzol lyield. Since the literature shows that the time consumed b thev initial decomposition of gaseous para s to form gaseous olefines is only a small fraction of the total time found to be required 'for forming a yield of benzol,'it is obvious that th@ same timetemperature lrelation ,is applicable to the treatment of gaseous olel'ines to form benzol and to all the simplerV paratlins which decompose into gaseous parailins and gaseous olefines. Methanebecauseof its great stability to heat is not converted into benzol under the time-temperature condi-- tions.

In view of the foregoing it is believed that the steps of the process and details of the ape paratus may be clearly understood by those skilled in the art and vfamiliar with such processes and apparatus and-.thatchanges may be made in the details disclosed Without departing from the spirit of the invention as `expressed in the claims.

What 'claimed and desired tolbe secured by Letters Patent is:

1. In a continuous process foi` the pyrocarbons m the said zone at the reformmg temlytic conversionpf normally gaseousaliphatic hydrocarbons to crude benzol, rapidly heatl f ing said gaseous hydrocarbons to reforming temperatures between-1250 and 1750 F. in a passageway of restricted cross-sectionalv area, passing'the heated gaseous hydrocarbons into an enlarged zone, maintaining without any addition of heat, the heated gaseous hydrocarbons in the said zone at the reforming temperature for an interval of time renheit, and t isthe time in minutes, and

then separating the crude benzol so produced.

2. In a continuous process for the pyrolytic conversion of normally gaseous ali hatic hydrocarbons to crude benzol, rapid y heating -said gaseous hydrocarbons to reforming temv4bons in .said zone for an interval of timesubstantially as expressed by the formula T=1245180 logmt,

wherein T is the temperature inpdegrees Fahrenheit, and -t is the time in minutes, tohen partially cooling the eilluentr gasesfrom said zone by indirect heat exchange with the inlet gases to saidpassageway, and linally separating the crude' benzol so produced.

3. )In a continuous process for the yrolytic conversion of'normallyxgaseous ali atic hydrocarbons to crude benzol, rapid y heating f' said gaseous hydrocarbons to reforming temperatures between 1250 andv 1750 F. in a passageway of restricted cross-sectional area, passing the heated gaseous hydrocarbons into an enlarged zone, maintaining without any addition of heat, the heated gaseous hydrocarbons in the said zone at the reforming tem-1 perature for an interval of time substantially as expressed by the 'formula p 'T=1245-180 logqot, A-

wherein` T is the temperature in degrees. Fahrenhe1t,`and t 1s t e tlme 1n mmutes,

then separating the crude benzol so produced,

and controllably returning portions of the residual crackedl gas to the mlet streaml of i,

`peraturesbetween 1250 'and 1750" F. in al Ypassage-way of restricted cross-sectional area,

- passing the heated gaseous hydrocarbons' into -an enlarged zone, maintaining without any addition of heat, the heated gaseous hydroperature for an interval of time substantially las expressed by the formula let gaseous hydrocarbons to said passageway,

separating the crude benzol so produced from A the' residual cracked as, and controllabl yreturning portions of t e residual cracke gas to the linlet stream of gaseous hydrocarbons entering said alssa eway. l

, G OR E G. OBERFELL.

JESSE A. GUYER. 

